Spring Transaction Manager不是线程安全的？

Question

I'm currently experiencing an unexpected behaviour with the Spring transaction manager: the same transaction is assigned to multiple threads. The scenario is a CXF webservice running in a Tomcat server. The service itself is a Spring bean (singleton). When sending many parallel requests (in my test I used 10) to the server it sometimes happens that two requests (running in different threads) work with the same transaction. Since the logic is designed to use one transaction per request this behaviour causes a faulty behaviour of the application.

Below my service class:

package ...clientsupport_v1;

import...

@WebService(targetNamespace = ...)
@Transactional(rollbackFor = MyException.class)
public class ClientSupportFacade extends AbstractServiceFacade implements ClientSupportService {

private static final Logger LOG = LoggerFactory.getLogger(ClientSupportFacade.class);

@Autowired
private HibernateTransactionManager transactionManager;

@Autowired
private ClientOrderImporter clientOrderImporter;

@Override
public Advice receiveClientPreAdvice(User user, PreAdvice preAdvice) throws MyException {
    LOG.debug("PreAdvice: " + preAdvice + ", Transaction: " + getTransactionId() + ", Thread: "
            + Thread.currentThread().getName());
...
    return advice;
}

private int getTransactionId() {
    return transactionManager.getSessionFactory().getCurrentSession().getTransaction().hashCode();
}

}

receiveClientPreAdvice is the method exposed as service operation.

When calling with multiple threads I get the following log lines:

2013-10-29 13:59:25.135 DEBUG e.h.p.s.c.c.ClientSupportFacade.receiveClientPreAdvice:42 - PreAdvice: PreAdvice [barcode=90000000002161, ...], Transaction: 420660542, Thread: http-bio-8080-exec-9
2013-10-29 13:59:25.135 DEBUG e.h.p.s.c.c.ClientSupportFacade.receiveClientPreAdvice:42 - PreAdvice: PreAdvice [barcode=90000000002163, ...], Transaction: 420660542, Thread: http-bio-8080-exec-8

As you can see two different objects have been received and two different threads are running. Yet the transaction is the same.

How can this happen? And - even more important - how can it be avoided?

Answer 1

From HibernateTransactionManager javadoc:

Binds a Hibernate Session from the specified factory to the thread, potentially allowing for one thread-bound Session per factory ... This transaction manager is appropriate for applications that use a single Hibernate SessionFactory for transactional data access, ...

It may be helpful to post your hibernate configuration but from your code, I can see you are logging getTransaction().hashCode() as Transaction ID assuming they refer to the same transaction object while hashCode() is not required to return different values for different objects. There can be 2 distinct transactions in progress that both have the same hash-code value.